Louis van Gaal has seen enough. Marouane Fellaini and James Wilson come off, Robin van Persie and Ander Herrera are on.

The wind and rain are really lashing down now. If it was 5-a-side and you'd just turned up you'd be thinking about staying in the car.

BBC Sport chief football writer Phil McNulty at Abbey Stadium

"Manchester United have clearly been told to up the tempo by Louis van Gaal here - but still no breakthrough and there is real expectancy from Cambridge's fans whenever they get the ball into that Manchester United penalty area. Head coach Richard Money will feel there is a real opportunity for joy going down that route.

"How United have missed the creation and endeavour of their captain Wayne Rooney."

Image source, Getty Images

David Shepherd: That is the goalkeeping equivalent of a worldie from the Cambridge 'keeper there to stop Falcao.

Get in touch at #bbcfacup, external, or text us on 81111 (UK only) - don't forget to say who you are and where you are texting from.

Image source, AP

The first half was ebb and flow but now it's a white tide breaking against the amber and black shore. Cambridge can't get out, and Manchester United finally look dangerous.

They scored at this point of the Yeovil game, but it took a screamer from Ander Herrera. Who can find one now?

James Wilson is booked for the visitors.

Former Cambridge United striker Steve Claridge
BBC Sport

"Best play of the night so far from Radamel Falcao. To take a touch like that and keep the ball away from the defender was excellent. A wonderful ball from Michael Carrick too - he played it hard and firm, but Falcao takes one touch, hits it hard but Chris Dunn just gets a touch on it and the ball goes over. Wonderful save."

Martin Keown
BBC Sport at the Abbey Stadium

"Finally a forward pass from Manchester United and Falcao was alive to it. That's much more positive from United, but it was a great save by Dunn in the Cambridge United goal. A moment of brilliance from the visitors and could it be all over for them though."

Louis van Gaal thought that was in. He was out of his seat. What a cracking stop.

Well there it is, the first real save Chris Dunn has had to make - and it is top class! One to remember as Radamel Falcao gets away from his marker, slides in to take a shot at goal from no more than 15 yards, and Dunn gets a big hand on it to turn over the top.

Brilliant save.

Image source, Getty Images

Former Cambridge United striker Steve Claridge
BBC Sport

"Both teams are adjusting to the conditions. Manchester United were playing into the wind in the first half and now it's Cambridge. It is blowing a 'hoolie' so to speak. We aren't affected in the commentary box but it is really windy out there. The penalty claim was just six of one and half a dozen of the other."

Cambridge whip a good ball into the box, Antonio Valencia is wrestling with Tom Elliott but there is nothing doing. They were both at it, it was even.

At the hour mark and Cambridge keeper Chris Dunn hasn't had to make one decent save.

Image source, Empics

In the last 10 minutes of today's game we will be asking you to vote for the FA man of the match award. We will let you know which three nominees BBC One co-commentator Martin Keown has selected for the award shortly, so stay tuned.

Martin Keown
BBC Sport at the Abbey Stadium

"The emphasis should be on Manchester United here. They are the Premier League team and we're not seeing enough from them."

James Wilson just threatens to break through the lines but he is mowed down by an excellent piece of covering from Michael Nelson. Any changes from the visitors? Louis van Gaal would make 11 if he could.

Former Cambridge United striker Steve Claridge
BBC Sport

"We've seen from decent play from Manchester United since the restart - intricate passing and good movement. But Cambridge United have stuck to their task and are making life difficult for the visitors. Cambridge have got men around the ball fantastically well - whenever United have possession in the middle of the pitch there is pressure immediately."

We might still be awaiting a goal in this one, but remember you can make sure you're first to hear about all the goals in the FA Cup this weekend with alerts sent to your phone via the BBC app.

The app is freely available from Google Play, external for Android devices, the App Store, external for iPhones, and the UK Amazon Kindle Fire Appstore, external.

Luke Chadwick is warming up. That's #657 in the book of FA Cup fairytales.

Manchester United completely dominating the ball but have offered nothing of note, apart from the Phil Jones taking a corner novelty act. Again his set-play is easily dealt with.

Martin Drake: I very much doubt Cambridge's income (see 20:52) is only £1.6m now they're back in the Football League. Presumably that is last year's figure.

Simon Vine: Manchester United's formation seems to be 3-4-1-1 at the moment. Cambridge handling the start of the second half very well. Could change by 80th minute though...

Innocent Adriko: Someone please tell Louis van Gaal the cure to his 'ass twitching' is to play faster. Slow passing build-up is so boring.

Get in touch at #bbcfacup, external, or text us on 81111 (UK only) - don't forget to say who you are and where you are texting from.

Martin Keown
BBC Sport at the Abbey Stadium

"Manchester United are asking some questions by putting some balls in the box, but Cambridge United have answered them so far."

A change on the wing from Cambridge, the outstanding name of Sullay KaiKai is replaced by the equally brilliantly-monikered Harrison Dunk.

Dunk joined from Bromley in 2011.